import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        // 读取电脑的价格
        int computerPrice = scanner.nextInt();

        int days = 0;
        int totalMoney = 0;

        // 使用循环计算小明需要多少天
        while (totalMoney < computerPrice) {
            days++;
            totalMoney += days;
        }

        // 输出结果
        System.out.println(days);

        scanner.close();
    }
}